The Liquid Line, Not the Big One, Sets Your Maximum Run
Carrier indexes maximum line length on the thin liquid line and on which unit sits higher. On a five ton, sixty feet of drop is the end of the table.
Two pipes leave your outdoor unit. One is fat and wrapped in black foam; the other is thin and bare. Every conversation about a line set is about the fat one — its diameter, whether it is a size small, what that costs.
Then you open the manufacturer’s piping page and the fat one is not in the table. The columns are the liquid line.
The limit is indexed on the pipe nobody looks at
Carrier’s residential product data sheets put the maximum run in a table with two axes: liquid line diameter down the side, vertical separation between the indoor and outdoor unit across the top. The number in the cell is the maximum total equivalent length the family is allowed at that combination.
The vapor line has its own table on the next page, and that one is about capacity you lose. This one is about whether the job is inside the acceptable range at all.
An air conditioner gets three diameters; a heat pump gets one
On the air conditioner sheets the small capacities have a choice, and the choice is expensive. These are the 26SCA5’s numbers with the outdoor unit below the indoor one, all with a TXV:
| Capacity | Liquid line | At 0–5 ft of separation | At 41–50 ft |
|---|---|---|---|
| 1.5 ton | 1/4 in | 150 ft | 75 ft |
| 1.5 ton | 3/8 in | 250 ft | 250 ft |
| 2 ton | 1/4 in | 75 ft | outside range |
| 2.5 ton | 1/4 in | 30 ft | outside range |
| 2.5 ton | 5/16 in | 175 ft | 100 ft |
| 2.5 ton | 3/8 in | 250 ft | 250 ft |
Read the 2.5 ton rows twice. Same model, same house, same day: 30 equivalent feet on quarter-inch copper, 250 on three-eighths. A quarter-inch liquid line turns that unit into a 30-foot machine, and more than five feet of height difference ends it entirely.
From 4 tons upward the choice disappears — the sheet lists 3/8 and nothing else — and every heat pump family read for this site publishes a single 3/8 row for every capacity in the range. The 25SCA5, the 27SCA5 and the 25HCE4 all do it that way.
That is not three sheets agreeing by chance. Carrier’s R-454B piping guideline prints the same table for the whole single- and two-stage range and labels every 1/4 and 5/16 inch row AC Only. The heat pump row is 3/8 inch, at every tonnage, with nothing beside it. On a heat pump there is nothing to get wrong here, because the manufacturer leaves nothing to choose.
Which unit is higher changes the answer completely
The air conditioner sheets carry two tables, one for the outdoor unit below the indoor unit and one for above. They are not the same table with the sign flipped.
| 26SCA5, 5 ton, 3/8 in liquid | Outdoor unit below | Outdoor unit above |
|---|---|---|
| Up to 20 ft | 250 ft | 250 ft |
| 31–40 ft | 190 ft | 250 ft |
| 51–60 ft | 110 ft | 250 ft |
| Past 60 ft | outside acceptable range | 250 ft, to 200 ft of separation |
Uphill, the height costs nothing all the way to the family’s ceiling. Downhill, it eats the allowance and then ends it. The 1.5 ton on a quarter-inch line is the same story read backwards: below the indoor unit it is allowed 150 feet at almost no separation and falls off the table past 50 feet, while above it, it is allowed 175 feet at 25 feet of separation and 250 at every greater height on the page.
The sheets publish this asymmetry. They do not explain it, and neither will this page — but it is the reason a quote that moves the condenser downhill to the far corner of the lot is a different question from one that moves it uphill.
Where the table simply ends
“Outside acceptable range” is printed as a pair of dashes, and it is the most important mark on the page. It is not a long-line application requiring accessories. It is not a capacity penalty. There is no cell to read.
On the 26SCA5, and identically on the 25SCA5 and 27SCA5 heat pumps, the five ton runs out at 60 feet of drop and the four ton at 70 — on the only liquid diameter either of them offers. If your indoor unit is in an attic and the pad is at the bottom of a sloping yard, that is a real constraint on a real house, and it is decided before anyone measures the fat pipe.
The same pipe sets the charge
The air conditioner sheets carry a third table for the liquid line, and it prices the run in refrigerant rather than in feet: 0.60 ounces per foot on a 3/8 inch line, 0.40 on 5/16, 0.27 on 1/4. The unit leaves the factory charged for 15 feet of 3/8 inch liquid line, and anything longer has to be added on site against a formula the sheet prints.
Two things follow that are worth knowing before a quote is signed.
The rate did not change with the refrigerant. The R-410A 24SCA5 and 24SPA6 and the R-454B 26SCA4 and 26SCA5 all print 0.60 ounces per foot on 3/8. Puron and Puron Advance, same number.
Fifteen feet is not a typical line set. A 40-foot run of 3/8 needs roughly another 15 ounces beyond what shipped in the box — on a system whose total charge is measured in single-digit pounds. Reusing a long existing line set is not a neutral act on the charge, and that is a conversation about the person doing the work, not about the copper.
The heat pump sheets read for this site publish no charge table at all. That is a gap in what is available to a reader, not permission to use the air conditioner’s number on a heat pump.
Two reference lengths on one page
One last trap, because it catches people comparing numbers between sections of the same document.
The published performance is rated with 25 feet of line set. The factory charge covers 15 feet of liquid line. Neither is the length your run will be, and they are not the same number as each other. Any sentence that starts “the unit is rated for…” has to say which of the two it means.
What this does not tell you
- It is Carrier, and mostly Carrier’s single-stage air conditioners. Six families read for this site print the same liquid-line table cell for cell across both refrigerants — the R-410A 24SCA4, 24SCA5, 24SPA6 and 24ABB3 and the R-454B 26SCA4 and 26SCA5 — which is unusually consistent for this site to find, and it still stops being true at the edge of that group. The 24VNA9 and the 25VNA8 cap every size at 100 equivalent feet, and other brands publish their own tables entirely.
- It is equivalent length, not measured length. Elbows and fittings count. The line-length guide has the rest of that, and it is an installer’s calculation either way.
- It says nothing about whether your copper can be reused. Length, diameter and cleanliness are separate questions, and the reuse answer is on the brand rules page.
What to ask your installer
- What diameter is my liquid line, and what does the sheet for the exact model you are quoting allow at that diameter?
- How much vertical separation is there between the two units, and is the outdoor unit above or below the indoor one?
- What charge adjustment are you calculating for the length of liquid line actually going in?
Questions people ask
Which pipe decides how far my outdoor unit can be?
The thin one. Carrier prints the maximum total equivalent length as a table indexed on liquid line diameter and on vertical separation — the fat insulated vapor line is not one of its columns. On a 26SCA5 at 2.5 tons the same unit is allowed 250 feet on a 3/8 inch liquid line and 30 feet on a 1/4 inch one.
Does it matter whether the outdoor unit is above or below the indoor one?
Yes, and it is the difference between a long run and no run at all. Carrier publishes two separate tables for its air conditioners. With the outdoor unit above, a five ton is allowed 250 equivalent feet at every separation up to 200 feet. With the outdoor unit below, the same five ton drops to 110 feet at 51 to 60 feet of separation and is outside the acceptable range past that.
Do I need to add refrigerant if the line set is long?
On these air conditioner families, yes, and the sheet gives the rate: 0.60 ounces per foot on a 3/8 inch liquid line, against a factory charge that covers 15 feet. The figure is identical on the R-410A and R-454B sheets — the refrigerant changed and the ounces per foot did not. The heat pump sheets read for this site do not publish the table at all.
Sources
- Carrier — Residential Piping and Long Line Guideline — Single-Stage and Two-Stage AC/HP Models Using R-454B Refrigerant . Read 2026-09-04.
- Carrier — 26SCA5 Comfort Series Single-Stage Air Conditioner with Puron Advance Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 26SCA4 Comfort Series Single-Stage Air Conditioner with Puron Advance Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 24SCA4 Comfort Series Single-Stage Air Conditioner with Puron Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 24SCA5 Comfort Series Single-Stage Air Conditioner with Puron Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 24SPA6 Performance Series Single-Stage Air Conditioner with Puron Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 24ABB3 Comfort 13 Air Conditioner with Puron Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 24AHA4 Performance Series Air Conditioner with Puron Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 25SCA5 Comfort Series Single-Stage Heat Pump with Puron Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 27SCA5 Comfort Series Single-Stage Heat Pump with Puron Advance Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 25HCE4 Comfort 14 Heat Pump with Puron Refrigerant — Product Data . Read 2026-09-02.
- Carrier — 24VNA9 Infinity 19VS Variable Speed Air Conditioner — Product Data . Read 2026-09-02.
- Carrier — 25VNA8 Infinity 18VS Variable Speed Heat Pump — Product Data . Read 2026-09-02.
This is a starting point, not an approval. Everything here is read from published manufacturer documents and dated, but only the licensed contractor who signs your installation can approve a specific system for your home and your local code. Take the citations on this page to them and ask.